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Full text of "Greenhouse thrips [Heliothrips hœmorrhoidalis Bouché]"

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[ssued Julj 15, 1912. 



U.S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ENTOMOLOGY -CIRCULAR No. 151. 

L. O. HOWARD. Entomologist and Chief of Bureau. 



Till-] GREENHOUSE Til IMPS. 



BY 



II. M. RUSSELL, 
Entomological As s i s taut. 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1012 




BUREA U OF ENTOMOLOGY. 

L. O. Howard, Entomologist and Chief of Bureau. 

C. L. Marlatt, Entomologist and Acting Chief in . l/*« nn of Chief. 

R. S. Clifton, Executive Assistant. 

W. F. Tastet,, Chief Clerk. 

F. H. Chittenden, in charge of truck crop and stored product insect investigations. 

A. D. Hopkins, in charge of forest insect investigations. 

W. D. Hunter, in charge of southern field crap insect investigations. 

F. M. Webster, in charge of cereal and forage insect investigations. 

A. L. Quaintance, tn charge of deciduous fruit insect investigations. 

E. F. Phillips, in charge of bee culture. 

D. M. Rogers, in charge ofpri venting spread of moths, fi< Id work. 

Roi i a P. Currie, in charge of editorial work. 

Mabel ColcObd, in charge of library. 

Truck Crop and Stored Product [nsect Investigations. 
F. II. Chittenden, in charge. 
H. M. Russell, C. H. Popenoe, Wm. B. Parker, II. 0. Marsh, M. M. High. 

Fred A. Johnston, John E. Graf, entomological assistants. 
1. J. Condit, collaborator in California. 
P. T. Cole, collaborator in tiilcirtiicr Virginia. 
W. N. Ord, collaborator in Oregon. 
Tims. ||. Jones, collaborator in PortoRico. 
Marion T. Van Horn, Pauline M. Johnson, preparators. 
ii 



Circular No. 151. 

United States Department of Agriculture, 

BUREAU OF ENTOMOLOGY. 
L. O. HOWARD, Entomologist and Chief of Bureau. 



THE GREENHOUSE THRIPS. 1 

I //. i lalis Bom I 

By II. M. Russell, 
Entomological Assistant. 

INTRODUCTION. 

The greenhouse thrips has been the cause "!' considerable injury to 
ornamentals during the past century, and where its presence is not 
suspected or treatment i- oeglected it will cause the utter ruin of cer- 
tain plain-, in the greenhouse, grown principally for the beauty of 
their foliage. Likewise in the more tropical sections of the United 
States, such as southern Florida and southern California, this insect 
causes L r ivat damage to some outdoor- plants. 

DESCRIPTION AM) I. UK HISTORY. 

The adult of this thrips i- a -mall, active insect aboul one twenty- 
fourth of an inch in lengt h and dark brown in color, with the tip of the 
decidedly lighter. The appearance of this insect is sufficiently 
illustrated in figure 1 to render a more detailed description unneces- 
sary. Tin- insect feeds on the foliage of the plant attacked and 
removes all the coloring matter, leaving the leaf white and. in severe 
cases of attack, dead. During this period the female deposits her eggs 
(fig. '_'. a within the leaf tissue and these hatch in the greenhouse in 
about eight day-. The larva which hatches from the egg is a minute 
white insecl <>( the shape indicated in figure _', 6 and c. During 1 his 
period, which requires from in to 20 days, varying with the tempera- 
ture, the larva' feed together in colonies on t he surface of t he leaf and 
remove i ho coloring matter in the same manner as do the adults. While 
ged in feeding, the larva exudes a large drop of reddish Quid from 

' Fora fuller technlc il treatment of this insect sec "The Greenhouse Thrips," Bnl. 64, Pt. VI, Bur. Km., 
V. S. Dept. Apr. 

r-Cir. 151 — 12 I 



2 THE GREENHOUSE THKIPS. 

the anal end of the body, and when this becomes too heavy it drops to 
the leaf surface and dries into a black dot. Where the insects are 
numerous these exudations produce a marked discoloration of the 
foliage. Upon becoming full grown the larvae change to the resting 
stages — prepupa and pupa (see fig. 3) — during which time they 
remain more or less motionless among the feeding young and take no 
food. These stages require periods of about four to six days, after 
which the adults emerge. Figure 5 shows a colony of pupse on a leaf 
of croton. The total time required for this insect from the time the 




Fig. 1. — Greenhouse thrips I Heliothrips hxmorrhoidalisy. Adult female, enlarged about 50 diam- 
eters, and greatly enlarged drawing of antenna underneath. (.Author's illustration.) 

egg is laid until the adult emerges ready to reproduce" its kind is from 
20 to 33 days, and as this insect continues active in the greenhouse 
the entire year many generations occur each year. 



OEIGIN AND DISTRIBUTION. 

Although this insect was first described from Europe and is there 
widely distributed, it is without doubt indigenous to tropical 
America. Tt lias been recorded in the open in St. Vincent and Bar- 
bados. This insect has been collected at Miami. Fla., on plants in 
the open in midwinter. At Stmt a Barbara, CaL, it caused consid- 
erable damage to ornamentals in one of the parks in November. 




rip 

larva, first stage; c, larva, full grown. 
All enlarged about 40 diameters. 
(Author's illustration.) 



THE < . K I I ffHOUS] I II KIPS. 3 

These records of occurrences at several localities in the Tropical and 
Lower Austral life zones of this country point strongly to tropical 
America as ii- original home. This i^ further strengthened because 
of its well-known babil of living in greenhouses, in many localities, 

upon exotic plant-- from the Tropics. 

From this habil it bas become widely dis- 
tributed in Europe and North America. 
1 ii Europe il i- recorded from England, 
Germany, Austria, Russia, Finland, 
France, Spain, and Italy. Jt is also 
known to occur in Australia and the 
I law aiian Islands. 

In this country it is recorded from 
Massachusetts, from several places in 
Michigan, and from Washington, D. ('.. 
Florida, and California. It bas been col- 
lected in Iowa and Pennsylvania and in 
the Barbados and the island of St. Vin- 
cent, British Wesl Indie-. 

Because of the fad that it bas been col- 
lected in such widely distanl places in all 
sections of thecounl r\ , we can safely saj that Helioihripsha morrhoidalis 
is generally distributed in greenhouses throughout the United Mate-. 

\ Vinti: AND EXTENT OF IX.UKY. 

Tin 1 damage caused by the greenhouse thrips to ornamental plants 

i- confined to the foliage entirely. 

in SO far a- I he aul hor is aw are, for 
he knOWS of QO recorded injury to 

the blossoms of theplantsnorhashe 

noticed any. The damage to fruits 
i- divided between injury to the 
foliage and t o the fruit itself. In- 
jury effected by the thrips is due to 
the method of feeding on the plants. 
Both adults and larvae obtain their 
food by puncturing the epidermis 
of the leaf or fruit w ith their sharp 
moul bparts, 1 and after lacerat big 
the tissue they suck out the vege- 
table matter ami plant juice- :i i 
the point of attack. The inseel 
then at tack- t he leaf or fruit in a new place, 50 that in time it becomes 
full of tiny pale -put- where the vegetable matter has been exl ract ed. 

> 1 Dr structure of mouthpaii Thrips," by Dudley Moultoti, Bui. 08, Pari I, Bur. 

Ent., V. 8. I 1 . 1907. 





eenhouse thri|>s: Prepupa on the left 
and pupa on the right. Enlarged about 40 >li- 
amcters. (Author's illustration.) 



THE GREENHOUSE THRIPS. 



In the case of infested plants, injury is noticed first to the older 
leaves and gradually, as these become badly infested, the injury 




FlG. 4.— Portion of leaf of crolou magnified to show pupa- of greenhouse thrips. (' » Iginal. I 

spreads until the young leaves are attacked, soon after unfolding. 
The infested leaves first show injury on the underside, where the 



GR] ENH0US1 I BRIPS. 



epidermis appears full of minute white spots. As attack continues 
the spots become more numerous and unite, forming blotches where 
the leaf is damaged. Figures I and 5 shows leaves of croton badly 







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Fio. 5. — Croton leavi . showii blea i. I black and brown spots due to reeding of the greenhouse 

thrips. (Original.) 

injured by this insect. The injur} then becomes apparent from the 
surface and develops a twisted and distorted aspect between the 
lateral veins, and is finally evidenced by wilted and dead area- 



THE GREENHOUSE THRIPS. 




Fig. 6. — Croton plant showing healthy appearance, Washington, D.C., December, 1911. (Original.) 



I ill GRI l N ih>i SE I HRTPS. 



around the edges of the leaf. 
In severe attacks the insects 
-prcad 1o the upper surface of 
the leaves, and in a shorl time 
this as well as the underside is 
nearly devoid of color. Both 
side- become thickly covered 
\\ ith minute drops of reddish 
fluid voided by the thrips, 
which gradually change to 
black. As the attack con- 
tinues, the leaves become limp 
and yellow and event ually drop 
off, so that the plants that are 
not treated to prevent injury ill 
many cases lose their entire foli- 
age. Figure 6 show- normal 
croton and figure 7 croton to- 
tally defoliated by the adults 
of this insect. 

This inseel injures plants in 
tw w ays: Firsl , a serious drain 
on the v itality of the plant is 
produced by the feeding of thou- 
sands of thrips, mp that the 
grow th is seriously checked and 
in neglected cases causes the 

death of the plant. Second, it 

destroys the beauty of the 
plants for ornament by event- 
ually despoiling them of I heir 
foliage. 

I n southern Florida thisinseel 
attacks the mango and alligator 
pear and causes greal injury \>y 
feeding on the foliage and it 
may also cause injury by feed- 
ing on the young I'm it and scar- 
ring it to a large extent. 

At Santa Barbara, Cal., this 
inseel occasionally becomes so 
abundant on orange t rees as to 
ruin the fruit and cause the en- 
tire foliage to drop. Theguava 
indusl ry t here has also suffered 
se\ erely from this inseel . 




Fig. 7.— Croton plant totally defoliated by ihcRrecn- 
bington, D.i , , 1912. 

Inal.) 



b THE GREENHOUSE THRIPS. 

FOOD PLANTS. 

The greenhouse thrips feeds on a large number of ornamental 
plants. In tins country it has been recorded as feeding on liliaceous 
plants, azalea, PeUea liastata, aspidium, croton, dahlia, phlox, ver- 
bena, pink, ferns, vines, cherry laurel (Prunus caroliniana) , laures- 
tina, palms, Ficus, and fuchsia. In California it has been found on 
raspberry, guava (Psidium guajava), and orange. Tins thrips 
damages the mango {Mangifera indica), alligator pear (Persea gra- 
tissima), and maple in Florida, and has been recorded from St. Vin- 
cent and the Barbados on cacao (Theobroma cacao), kola, and the date 
palm (Phoenix dactylifera) . In Europe this thrips has been recorded 
as preying upon serides, azalea, begonia, camarotes, cattleya, crinums, 
dendrobium, eucharis, Ficus, grape, lselia, lefortia, marcintacia, 
pancratium, phalenopsis, banana, and viburnum. In Australia it is 
recorded as occurring on different species of eucalyptus. 

REMEDIES. 

For the treatment of tins pest there are a number of good remedies. 
The question as to the best method to employ depends upon the size 
of the greenhouse infested and upon the experience of the person 
engaged in treating the insect. 

Fumigation with nicotine papers. — Any of the standard fumigating 
papers will give good results against tins pest if they are strictly fresh 
and kept tightly sealed. Fumigation should be done at night in a 
moist atmosphere, and the papers should be used at the rate of about 
2 sheets for eveiy 1,000 cubic feet of space. Early in the morning 
the house should be opened and thoroughly aired. 

Fumigation with nicotine liquid extracts. — Liquid extracts of nico- 
tine offer one df the best methods of greenhouse fumigation and 
against tins pest are very successful. Those made up of 40 per cent 
nicotine should be used at the rate of 1 ounce to eveiy 1,000 cubic 
feet of space and the weaker solutions at greater strengths. The 
preparation should be evaporated over small lamps or stoves, and 
to prevent scorching should be diluted with water, approximately 
two-thirds. Fumigation should he carried on at night in a moist 
atmosphere, and the greenhouse should remain closed all night. 

Fumigation with hydrocyanic-acid gas. 1 — When fumigating with 
hydrocyanic-acid gas great care should he taken, as this gas is fatal 
to all animal life. The work must he conducted at night, and the 
plants should have dry foliage. In treating this insect, use from 0.01 
to 0.05 gram of potassium cyanid per cubic foot for from two hours 
to all night, the strength and length of exposure varying according 
to the tightness of the house and the kind of plants that are being 

1 For complete directions for the use of hydrocyanic-acid gas, see Cirs. 37 and 57, Bur. Ent., U.S. Dept. Agr. 



l in: GRE1 N KOUS] THRIPS. 9 

treated, as there is considerable difference between various plants in 
their resisting power to this gas. 

Spraying with nicotim liquids. -Nicotine extracts diluted with 
water, if carefully applied to plants, will kill large numbers of the 
greenhouse thrips, bul thegreal objection is thai many of the in 
are not hit by the spray, and therefore the plants become reinfe ted 
in a short time. 

Spraying with kerosem emulsion? It is quite possible that kerosene- 
emulsion -ptay will be effective against the greenhouse thrips when 
used at the strength of 1 part of stock to 10 pan- of water, and it 
costs considerably less and is more readily obtained than the nicotine 
preparations. It should be very carefully prepared and used experi- 
mentally at first until the effect on the foliage of the different plants 
is noted. ( 'are should also be taken to prevent quantities of emulsion 
from collecting around the roots. 

Water spray. Frequent treatment with a still' spray of water from 
a garden hose or syringe will tend to keep tins insed down, bul unless 
there are only a few plant- it would he better to use one of the other 
remedies. 

Any treatment For this insect should be repeated in from 7 to 10 
day- to destroy the young larvie that have hatched from the e<_r'_ r -. 
This should be sufficient, but it may be besl to give a third treatmenl 
in another w cek or two. 

Treatment of trees in th open. — In the case of injury to the various 
subtropical fruits it is recommended to spray the foliage thoroughly 
with a nicotine spray. A tobacco extract of 2\ per cent of nicotine 
sulphate, diluted at the rate of 1 part to (it) parts in a 6 per cent 
distillate-oil emulsion, bas given such good results againsl the pear 
thrips that this treatment should be tried. 2 

Approved : 

.1 wii - Wilson, 

Seen tary of . igricultun . 

\\ ashing roN, D. ( '.. April 19, 191 .'. 

i For the method of making emulsioi Bulletin 127, or Cir. 80, Bur. Ent.,TJ.S. Dept. \-.t. 

> Full directions for mixing this spray are given in Cir. 131, Bur. Km.. I*. .-. Dept. \ 



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